Lithium-based batteries are widely used in consumer electronics, such as laptop computers, camcorders, cameras, and cell phones, and are increasingly being considered for applications in electric vehicles, including electric vehicles (EVs), hybrid electric vehicle (HEVs), and plug-in hybrid-electric vehicles (PHEVs). However, their use has been largely obviated due to safety concerns related to formation of lithium dendrites, which generally originate at the anode and spread across to the cathode during repeated charge-discharge cycling. When an electric current passes through the dendrites, an internal short-circuit with localized overheating is generally the result. Since volatile liquid organic electrolytes are generally used in lithium batteries, local overheating can result in combustion, with dangerous consequences.
Solid Li ionic conductors, such as polymer, glass, and crystal, have been considered as promising candidates for electrolytes in lithium metal batteries, owing to their inherent advantages in terms of safety and device fabrication. For example, solid electrolytes with mechanical modulus above lithium metal can serve as rigid barriers that prevent lithium dendrites from crossing the inter-electrode space, thereby preventing the battery from short-circuiting. However, their ionic conductivities at room temperature are generally significantly below the optimal level for efficient battery operation. Organic liquid electrolytes, in contrast, generally possess superior ionic conductivities with fast ionic transport properties, which makes organic liquid electrolytes desirable for commercial use in Li-ion batteries. However, as discussed above, dendrite formation is known to occur with use of liquid electrolytes, and the liquid electrolytes may combust as a result of short circuiting from dendrite formation. Aside from problems associated with dendrite formation, lithium batteries employing organic liquid electrolytes are also subject to electrolyte leakage. Sodium-ion batteries are also gaining increasing interest as cost-effective alternatives with greater safety potential. However, sodium dendrites are also a known concern. Thus, there would be a significant benefit in an electrolyte that could provide the beneficial aspects of both solid and liquid electrolytes while mitigating each of their drawbacks.